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202
as compared with less sanitary or unhealthy districts the reduction
of small-pox mortality would be greater among the young than
among the adult population.
That this is actually the case has been shown in section 198
of our colleagues' report. It is true that the admitted fact is
there referred to the greater opportunity afforded to town dwellers
of catching small-pox and catching it early. We are, however,
quite unable to agree with our colleagues that overcrowding upon
area or within dwellings ought not to be regarded as an insanitary
circumstance, and the fact remains that sanitation or environment,
or at any rate means other than vaccination, exert a profound
influence, not only upon the amount of small-pox mortality, but
also upon its age distribution.
That vaccination cannot be accepted as an adequate explanation
of the shifting of age incidence of fatal small-pox, or at any
rate as the sole explanation of the phenomenon, is proved by the
fact that a very considerable shifting has been observed in the
case of deaths from small-pox of those certified to have been
unvaccinated. Now it is only since the year 1881 that the
Registrar-General has classified the deaths from small-pox into
three groups—the vaccinated, the unvaccinated, and the "not
stated." Confining our attention to the unvaccinated, we learn
that of 3,746 deaths in the years 1881-93, 1,483 were under five
years of age, or 39.5 per cent. Now it has been repeatedly stated
that the normal proportion of deaths from small-pox under five
to the total Small-Pox deaths last century (and vaccination apart)
may be taken as 80 per cent. What, then, is the explanation of
the reduction of the proportion by one-half? It has indeed been
alleged that vaccination may indirectly have produced the effect
by reducing the amount of small-pox or controlling its virulence.
If this explanation be regarded as satisfactory, it may equally be
urged that any measures, such as isolation and more efficient
precautions against contagion, may also exert a powerful influence,
not only upon the amount of small-pox, but also upon its age
distribution amongst the unvaccinated.